Variable camshaft

ABSTRACT

A variable camshaft includes a base shaft, an axially movable structure, and an actuator. The axially movable structure includes a plurality of lobe packs and at least one barrel cam defining a control groove having an engagement region, a first shift region, a balancing region, a second shift region and a disengagement region. The actuator includes at least one pin operatively configured to move relative to the actuator body between a retracted position and an extended position into the control groove. The axially movable structure moves axially relative to the base shaft the pin is in the extended position and is at least partially disposed in one of the first or second shift regions of the control groove.

TECHNICAL FIELD

The present disclosure relates to vehicle engines and more particularly, variable camshafts for vehicle engines.

BACKGROUND

Some internal combustion engines include an adjustable or slideable camshaft assembly. The camshaft assembly includes a base camshaft that is rotatable about a cam axis. An axially moveable structure (which includes a lobe pack) is slideably attached to the camshaft for axial movement along the cam axis relative to the camshaft. The lobe pack is rotatable with the camshaft about the cam axis. The lobe pack is moveable between at least two different axial positions along the cam axis. Each different position of the lobe pack presents a different cam lobe having a different lobe profile for engaging a respective valve stem of the engine. Accordingly, by adjusting the position of the lobe pack, the cam profile that each valve stem of the engine follows may be changed.

The lobe pack includes a barrel cam 114 (shown in FIG. 1) that defines a control groove 118 disposed annularly about the cam axis 140. A first shifting pin 116 is moveable in a direction 123 transverse to the cam axis 140. The first shifting pin 116 moves between an engaged position (shown in FIG. 1A) and a disengaged position (shown in FIG. 1B). When disposed in the engaged position, the first shifting pin 116 is engaged with the control groove 118, such that interaction between the first shifting pin 116 and the control groove 118 moves an axially moveable structure (shown schematically as element 120) which includes the lobe pack axially along the cam axis 140 relative to the base shaft 128, in a first axial direction 134 and into a first axial position, as the axially moveable structure/lobe pack 120 rotates about the cam axis 140 with the base shaft 128. Similarly, a second shifting pin (not shown) may be moveable in a direction transverse to the cam axis 140. The second shifting pin moves between an engaged position and a disengaged position. When disposed in the engaged position, the second shifting pin may be engaged with the control groove 118, such that interaction between the second shifting pin and the control groove 118 moves the axially moveable structure 120 (having the lobe packs) axially along the cam axis 140 relative to the camshaft 126, in a second axial direction 135 and into a second axial position, as the lobe pack rotates about the cam axis 140 with the camshaft 126. When disposed in their respective disengaged positions, the first shifting pin 116 and the second shifting pin are disengaged from the control groove 118 such that the axially moveable structure 120 remains positionally fixed along the cam axis 140, relative to the base shaft 128, as the axially movable structure/lobe pack 120 rotates about the cam axis 140 with the base shaft 128. The axially moveable structure 120 having a lobe pack may remain positionally fixed relative to the camshaft 126 via an interlocking detent ball and detent groove retention mechanism disposed on the lobe pack and the base shaft 128 respectively.

During normal operation, the base shaft 128 and the axially movable structure/lobe pack 120 only rotate about the cam axis 140 in a first rotational direction. The control groove 118 is shaped to engage the first shifting pin 116 and the second shifting pin (not shown), to guide the axially movable structure/lobe pack 120 between the first axial position and the second axial position along the cam axis 140 respectively, when the base shaft 128 and the axially movable structure/lobe pack 120 are rotating in the first rotational direction. However, the wall 132 in the ejection region 130 of the control groove 118 may experience failure due to the loads that either the first or second shifting pin imposes on the barrel cam wall 132 when the pin 116 transitions from the engagement groove 122 through the shifting groove 124 and into the ejection groove 130. It is understood that design constraints limit the width of the barrel cam 114. Therefore, the relative axial movement of the pin 116 to the barrel cam—from the first position to the second position imposes significant loads on the outer wall 132 of the barrel cam 114. As shown in FIGS. 1A-1B, the outer wall 132 in the ejection region 130 of the control groove 118 is rather thin due to the required axial movement and the design constraints for the barrel cam width. Accordingly, the outer wall 132 may be prone to failure when the pin 116 moves to the ejection groove and engages with the outer wall in the ejection groove.

Accordingly, there is a need for an improved camshaft assembly which can sustain significant loads resulting from the engagement between barrel cam 114 and the actuator pin 116.

SUMMARY

The present disclosure provides a variable camshaft having a base shaft, an axially movable structure, and an actuator. The axially movable structure includes a plurality of lobe packs and at least one barrel cam defining a control groove having an engagement region, a first shift region, a balancing region, a second shift region and a disengagement region. The actuator includes at least one pin operatively configured to move relative to the actuator body between a retracted position and an extended position into the control groove. The axially movable structure moves axially relative to the base shaft the pin is in the extended position and is at least partially disposed in one of the first or second shift regions of the control groove.

The invention and its particular features and advantages will become more apparent from the following detailed description considered with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present disclosure will be apparent from the following detailed description of preferred embodiments, and best mode, appended claims, and accompanying drawings in which:

FIG. 1A shows a prior art barrel cam on a base shaft where the first shifting pin is in the engagement position.

FIG. 1B illustrates the prior art barrel cam of FIG. 1A where the first shifting pin is in the disengagement position.

FIG. 2 illustrates a schematic diagram of a vehicle including an engine assembly.

FIG. 3 illustrates a schematic side view of a portion of the camshaft assembly and two engine cylinders where the lobe packs of the camshaft assembly are in a first position.

FIG. 4 illustrates a schematic side view of a portion of the camshaft assembly and two engine cylinders where the lobe packs of the camshaft assembly are in a second position.

FIG. 5 illustrates a schematic diagram showing the various regions of the control groove for the camshaft of the present disclosure.

FIG. 6A illustrates a first shifting pin in an engagement region in the camshaft of the present disclosure.

FIG. 6B illustrates a first shifting pin in a balancing region in the camshaft of the present disclosure.

FIG. 6C illustrates a first shifting pin in an ejection region in the camshaft of the present disclosure.

Like reference numerals refer to like parts throughout the description of several views of the drawings.

DETAILED DESCRIPTION

The exemplary embodiments described herein provide detail for illustrative purposes, and are subject to many variations in composition, structure, and design. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but these are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present disclosure. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting.

Those having ordinary skill in the art will recognize that terms such as “above,” “below,” “upward,” “downward,” “top,” “bottom,” etc., are used descriptively for the figures, and do not represent limitations on the scope of the disclosure, as defined by the appended claims. Furthermore, the disclosure may be described herein in terms of functional and/or logical block components and/or various processing steps. It should be realized that such block components may be comprised of any number of hardware, software, and/or firmware components configured to perform the specified functions.

Referring to the drawings, wherein like reference numbers correspond to like or similar components throughout the several figures, FIG. 2 schematically illustrates a vehicle 10 such as a car, truck or motorcycle. The vehicle 10 includes an engine assembly 12. The engine assembly 12 includes an internal combustion engine 14 and a control module 16, such an engine control module (ECU), in electronic communication with the internal combustion engine 14. The terms “control module,” “module,” “control,” “controller,” “control unit,” “processor” and similar terms mean any one or various combinations of one or more of Application Specific Integrated Circuit(s) (ASIC), electronic circuit(s), central processing unit(s) (preferably microprocessor(s)) and associated memory and storage (read only, programmable read only, random access, hard drive, etc.) executing one or more software or firmware programs or routines, combinational logic circuit(s), sequential logic circuit(s), input/output circuit(s) and devices, appropriate signal conditioning and buffer circuitry, and other components to provide the described functionality. The control module 16 may have a set of control routines executed to provide the desired functions. Routines are executed, such as by a central processing unit, and are operable to monitor inputs from sensing devices and other networked control modules, and execute control and diagnostic routines to control operation of actuators. Routines may be executed based on events or at regular intervals.

The internal combustion engine 14 includes an engine block 18 defining a plurality of cylinders 20A, 20B, 20C, and 20D. In other words, the engine block 18 includes a first cylinder 20A, a second cylinder 20B, a third cylinder 20C, and a fourth cylinder 20D. Although FIG. 1 schematically illustrates four cylinders, the internal combustion engine 14 may include more or fewer cylinders. The cylinders 20A, 20B, 20C, and 20D are spaced apart from each other but may be substantially aligned along an engine axis E. Each of the cylinders 20A, 20B, 20C, and 20D is configured, shaped and sized to receive a piston (not shown). The pistons are configured to reciprocate within the cylinders 20A, 20B, 20C, and 20D. Each cylinder 20A, 20B, 20C, 20D defines a corresponding combustion chamber 22A, 22B, 22C, 22D. During operation of the internal combustion engine 14, an air/fuel mixture is combusted inside the combustion chambers 22A, 22B, 22C, and 22D in order to drive the pistons in a reciprocating manner. The reciprocating motion of the pistons drives a crankshaft (not shown) operatively connected to the wheels (not shown) of the vehicle 10. The rotation of the crankshaft can cause the wheels to rotate, thereby propelling the vehicle 10.

In order to propel the vehicle 10, an air/fuel mixture should be introduced into the combustion chambers 22A, 22B, 22C, and 22D. To do so, the internal combustion engine 14 includes a plurality of intake ports 24 fluidly coupled to an intake manifold (not shown). In the depicted embodiment, the internal combustion engine 14 includes two intake ports 24 in fluid communication with each combustion chamber 22A, 22B, 22C, and 22D. However, the internal combustion engine 14 may include more or fewer intake ports 24 per combustion chamber 22A, 22B, 22C, and 22D. The internal combustion engine 14 includes at least one intake port 24 per cylinder 20A, 20B, 20C, 20D.

The internal combustion engine 14 further includes a plurality of intake valves 26 configured to control the flow of inlet charge through the intake ports 24. The number of intake valves 26 corresponds to the number of intake ports 24. Each intake valve 26 is at least partially disposed within a corresponding intake port 24. In particular, each intake valve 26 is configured to move along the corresponding intake port 24 between an open position and a closed position. In the open position, the intake valve 26 allows inlet charge to enter a corresponding combustion chamber 22A, 22B, 22C, or 22D via the corresponding intake port 24. Conversely, in the closed position, the intake valve 26 precludes the inlet charge from entering the corresponding combustion chamber 22A, 22B, 22C, or 22D via the intake port 24.

As discussed above, the internal combustion engine 14 can combust the air/fuel mixture once the air/fuel mixture enters the combustion chamber 22A, 22B, 22C, or 22D. For example, the internal combustion engine 14 can combust the air/fuel mixture in the combustion chamber 22A, 22B, 22C, or 22D using an ignition system (not shown). This combustion generates exhaust gases. To expel these exhaust gases, the internal combustion engine 14 defines a plurality of exhaust ports 28. The exhaust ports 28 are in fluid communication with the combustion chambers 22A, 22B, 22C, or 22D. In the depicted embodiment, two exhaust ports 28 are in fluid communication with each combustion chamber 22A, 22B, 22C, or 22D. However, more or fewer exhaust ports 28 may be fluidly coupled to each combustion chamber 22A, 22B, 22C, or 22D. The internal combustion engine 14 includes at least one exhaust port 28 per cylinder 20A, 20B, 20C, or 20D.

The internal combustion engine 14 further includes a plurality of exhaust valves 30 in fluid communication with the combustion chambers 22A, 22B, 22C, or 22D. Each exhaust valve 30 is at least partially disposed within a corresponding exhaust port 28. In particular, each exhaust valve 30 is configured to move along the corresponding exhaust port 28 between an open position and a closed position. In the open position, the exhaust valve 30 allows the exhaust gases to escape the corresponding combustion chamber 22A, 22B, 22C, or 22D via the corresponding exhaust port 28. The vehicle 10 may include an exhaust system (not shown) configured to receive and treat exhaust gases from the internal combustion engine 14. In the closed position, the exhaust valve 30 precludes the exhaust gases from exiting the corresponding combustion chamber 22A, 22B, 22C, or 22D via the corresponding exhaust port 28.

As discussed in detail below, intake valve 26 and exhaust valve 30 can also be generally referred to as engine valves 66 (FIGS. 3-4) or simply valves. Each valve 66 (FIGS. 3-4) is operatively coupled or associated with a cylinder 20A, 20B, 20C, or 20D (shown in FIG. 2). Accordingly, the valves 66 (FIGS. 3-4) are configured to control fluid flow (i.e., air/fuel mixture for intake valves 26 and exhaust gas for exhaust valve 30 to the corresponding cylinder 20A, 20B, 20C, or 20D. The valves 66 operatively coupled to the first cylinder 20A can be referred to as first valves. The valves 66 operatively coupled to the second cylinder 20B can be referred to as second valves. The valves 66 operatively coupled to the third cylinder 20C can be referred to as third valves. The valves 66 operatively coupled to the fourth cylinder 20D can be referred to as fourth valves.

As shown in FIG. 2, the engine assembly 12 further includes a valvetrain system 32 configured to control the operation of the intake valves 26 and exhaust valves 30. Specifically, the valvetrain system 32 can move the intake valves 26 and exhaust valves 30 between the open and closed positions based at least in part on the operating conditions of the internal combustion engine 14 (e.g., engine speed). The valvetrain system 32 includes one or more camshaft assemblies 33 substantially parallel to the engine axis E. In the depicted embodiment, the valvetrain system 32 includes two camshaft assemblies 33. One camshaft assembly 33 is configured to control the operation of the intake valves 26, and the other camshaft assembly 33 can control the operation of the exhaust valves 30. It is contemplated, however, that the valvetrain system 32 may include more or fewer camshaft assemblies 33.

In addition to the camshaft assemblies 33, the valvetrain assembly 32 may include a plurality of actuators 34A, 34B, 34C, 34D, such as solenoids, in communication with the control module 16. Note that two additional actuators (not shown) may be implemented for the exhaust lobe on second cylinder and for the exhaust lobe on the third cylinder. The actuators 34A, 34B may be electronically connected to the control module 16 and may therefore be in electronic communication with the control module 16. The control module 16 may be part of the valvetrain system 32. In the depicted embodiment, the valvetrain system 32 includes first, second, third, and fourth actuators 34A, 34B, 34C, 34D. The first actuator 34A is operatively associated with the first and second cylinders 20A, 20B and can be actuated to control the operation of the intake valves 26 of the first and second cylinders 20A, 20B. The second actuator 34B is operatively associated with the first and second cylinders 20A, 20B and can be actuated to control the operation of the intake valves 26 of the first and second cylinders 20A, 20B. The third and fourth actuators 34C and 34D is operatively associated with the third and fourth cylinders 20C and 20D and can be actuated to control the operation of the intake valves 26 of the third and fourth cylinders 20C and 20D. The fifth actuator 34E is operatively associated with the second cylinder 20B and can be actuated to control the operation of the exhaust valves 30 of the second cylinder 20B. The sixth actuator 34F is operatively associated with the third cylinders 20C and can be actuated to control the operation of the exhaust valves 30 of the third cylinders 20C. The actuators 34A, 34B, 34C, 34D, 34E, 34F and control module 16 may be deemed part of the camshaft assembly 33.

With reference to FIG. 3, the camshaft assembly 33 includes at least one axially movable structure 44 with lobe packs 46A, 46B, 46C, 46D. Though FIG. 3 shows only one axially movable structure 44, it is contemplated that the camshaft assembly 33 may include more axially movable structures 44. The first and second lobe packs 46A, 46B are operatively associated with one cylinder 20A of the engine 14 (FIG. 1), while the third lobe pack 46C is operatively associated with another cylinder 20B of the engine 14. The axially movable structure 44 may also include more or fewer than four lobe packs 46A, 46B, 46C, 46D. Regardless of the number of lobe packs, each axially movable structure 44 may, but not necessarily, have a single barrel cam 56. Accordingly, the camshaft assembly 33 may only include one barrel cam 56 for every two cylinders 20A, 20B. Because the barrel cam 56 interacts with one actuator 34A to move the axially movable structure 44 relative to the base shaft 35, the camshaft assembly 33 may only include a single actuator 34A (or 34B) for every two cylinders 20A, 20C. In other words, the camshaft assembly 33 may have a single actuator 34A for every two cylinders 20A, 20B. With the illustrated control groove configuration, it is useful to have only two barrel cams 56A and 56B used in conjunction with corresponding actuators 34A and 34B for every two cylinders 20A, 20B.

As discussed above, the first, second, third, and fourth lobe packs 46A, 46B, 46C, 46D each include one group of cam lobes 50. Each group of cam lobes 50 may include a first cam lobe 54A, a second cam lobe 54B, and a third cam lobe 54C. The first cam lobe 54A may have a first maximum lobe height H1. The second cam lobe 54B has a second maximum lobe height H2. The third cam lobe 54C has a third maximum lobe height H3. The first, second, and third maximum lobe heights H1, H2, H3 may be different from one another. It is understood that while three cam lobes per group 50 are illustrated in the present non-limiting example, the variable camshaft 33 of the present disclosure may have two or more cam lobes per group.

Referring back to the embodiment depicted in FIG. 3, the first, second, and third cam lobes 54A, 54B, 54C of the first and second lobe packs 46A, 46B have different maximum lobe heights, but the first and second cam lobes 54A, 54B of the third lobe pack 46C have the same maximum lobe heights. In other words, the first maximum lobe height H1 may be equal to the second maximum lobe height H2. Alternatively, the first maximum lobe height H1 may be different from the second maximum lobe height H2. Accordingly, it is understood that it is entirely possible for the first, second and third cam lobes 54A, 54B, 54C to have different lifts on lobe packs 46A, 46B, 46C, and 46D due different lift heights H1, H2, H3. Referring back to the figures, the maximum lobe heights of the cam lobes 54A, 54B, 54C corresponds to the valve lift of the intake and exhaust valves 26, 30. The camshaft assembly 33 can adjust the valve lift of the intake and exhaust valves 26, 30 by adjusting the axial position of the cam lobes 54A, 54C, 54D relative to the base shaft 35. This can include a zero lift cam profile if desired. The cam lobes 54A, 54B, 54C of each group of cam lobes 50 are disposed in different axial positions along the longitudinal axis X.

With reference to FIGS. 3-4, the lobe packs 46A, 46B, 46C, 46D can move relative to the base shaft 35 between a first position (FIG. 3), and a second position (FIG. 4) via the shifting pin 64A or 64B and the control groove 60A defined in barrel cam 56A. To do so, the barrel cam 56A physically interacts with the actuator 34A which causes the axially moveable structure 44 to move in direction 210 Similarly, actuator 34B with shifting pin 64C or 64D engage with the control groove 60B defined in barrel cam 56B which causes the axially moveable structure to move in the opposite direction 212. As discussed above, the barrel cams 56A, 56B each include a barrel cam body 58 and defines a control groove 60A, 60B extending into the barrel cam body 58. The control groove 60A, 60B is elongated along at least a portion of the circumference of the respective barrel cam 56A, 56B.

Referring now to FIG. 5 and FIGS. 6A-6C, the barrel cam 56 of the present disclosure defines a control groove 60 in the barrel cam 56 as shown. For purposes of the FIGS. 5, 6A-6C, pin 64 may be either first pin 64A or pin 64B (shown in FIGS. 3 and 4). In the non-limiting example shown in FIG. 5, various regions of the control groove 60 are shown. Such regions include: (1) pin engagement region 62; (2) first shift region 63; (3) balancing region 66; (4) second shifting region 68; and (5) disengagement region 70. The camshaft 33 of the present disclosure therefore includes a barrel cam 56 which may include two shifting regions—first shift region 63 and second shift region 68. The goal of the two-step design using two shifting regions is to reduce the loads 82 imposed on outer wall 86 of the control groove 60 wall (after the pin 64 travels through the first shifting region 63) thereby enhancing product durability.

The general idea of the present disclosure is that the actuator pin 64 will enter the control groove 60 in the pin engagement region 62 and the lobe pack (and the axially moveable structure shown schematically as 44) will shift when the pin 64 contacts the ‘first push wall’ 72) at a first entry area 76 and then travels through the first shift region 63. It is understood that the first entry area 76 is the area where the engagement region 62 transitions into the first shift region 63. After completing travel through the first shift region 63, the pin enters the balancing region 66 and may impact the outer catch wall 86 in the balancing region. As shown in FIG. 6B, the thickness 88 of the outer catch wall 86 is relatively substantial such that the outer catch wall 86 has a thickness 88 which is greater than the disengagement catch wall thickness 96. Therefore, the outer catch wall 86 can withstand the impact loads 82 from the pin 64 after the pin comes out of the first shift region 63. Accordingly, the present disclosure provides for a more durable variable camshaft.

Accordingly, due to lack of engagement with first push wall 72 and an impact engagement with outer catch wall 86, the pin 64 no longer experiences any loads. Therefore, the pin 64 becomes “axially stationary” as the pin 64 travels straight through the balancing region 66 of the control groove 60. It is understood that axially stationary means that the actuator pin 64 will no longer be urged against a sidewall (first push wall 72) of the groove 60 given that the pin 64 is in a region where the control groove 60 has a straight path and the pin 64 is not urged against the first and second push walls 72, 73 of the control groove 60.

The actuator pin 64 may then cause the axially moveable structure to make a second shift further along the base shaft 35 via second shift region 68 within the same groove 60 where the pin 64 again contacts the second push wall 73 at a second entry area 78 and therefore urges the axially movable structure 44 along the base shaft in second shifting region 68. It is understood that the second entry area is the area where the balancing region transitions into the second shift region 68. As the pin 64 travels through the control groove 60 in the second shift region 68, the barrel cam 56 and its associated axially movable structure 44 is moved further along the base shaft 35 until the pin 64 reaches its final axial location at the in the disengagement region 70 after engaging with outer disengagement wall 92. Upon progressive travel of the pin 64 into the disengagement region 70, the pin 64 becomes axially stationary again given that the pin 64 is no longer urged against the second push wall 73 and therefore, the pin 64 may be disengaged from the barrel cam 56 by retraction into the actuator.

Given that the pin's movement from the engagement region 62 to the disengagement region 70 is performed in two steps via the first shift region 63 and the second shift region 68 (shown in FIGS. 6B and 6C respective), the strain experienced by the barrel cam 56 due to the actuator pin 64 is reduced due to the increased thickness 88 of the outer catch wall 86. Moreover, this configuration of the present disclosure maintains the same width of the barrel cam while significantly improving durability. It is understood that packaging issues are critical with respect to camshafts and therefore, design constraints limit the width of the barrel cam 56. Accordingly, the barrel cam 56 experiences reduced the stress on the control groove 60 as well as increased barrel cam 56 durability. It is understood that this two-step configuration can be applied to all control grooves and may be very effective in increasing the durability of high mass lobe packs with low packaging space.

The detailed description and the drawings or figures are supportive and descriptive of the disclosure, but the scope of the disclosure is defined solely by the claims. While some of the best modes and other embodiments for carrying out the claimed teachings have been described in detail, various alternative designs and embodiments exist for practicing the disclosure defined in the appended claims.

While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the disclosure as set forth in the appended claims and the legal equivalents thereof. 

What is claimed is:
 1. A variable camshaft comprising: a base shaft; an axially movable structure mounted on the base shaft, the axially movable structure being axially movable relative to the base shaft and being rotationally fixed to the base shaft, wherein the axially movable structure includes a plurality of lobe packs and at least one barrel cam defining a control groove having an engagement region, a first shift region, a balancing region, a second shift region and a disengagement region having a disengagement catch wall; an actuator including an actuator body and at least one pin movably coupled to the actuator body, the at least one pin being configured to move relative to the actuator body between a retracted position and an extended position; and wherein the axially movable structure is configured to move axially relative to the base shaft when the base shaft rotates about a longitudinal axis and the at least one pin is in the extended position and at least partially disposed in one of the first or second shift regions of the control groove.
 2. The variable camshaft as defined in claim 1 wherein the balancing region is defined in the control groove between the first and second shift regions.
 3. The variable camshaft as defined in claim 2 wherein the at least one pin is operatively configured to be axially stationary in the balancing region.
 4. The variable camshaft as defined in claim 3 wherein the first shift region defines a first push wall operatively configured to engage with the at least one pin thereby moving the axially moveable structure along the base shaft.
 5. The variable camshaft as defined in claim 4 wherein the balancing region defines an outer catch wall operatively configured to engage with the pin upon impact, the outer catch wall having a thickness greater than the thickness of the disengagement catch wall.
 6. The variable camshaft as defined in claim 4 wherein the second shift region defines a second push wall operatively configured to engage with the at least one pin thereby moving the axially moveable structure along the base shaft.
 7. The variable camshaft as defined in claim 6 wherein a first entry area is defined where the engagement region transitions into the first shift region.
 8. The variable camshaft as defined in claim 7 wherein a second entry area is defined where the balancing region transitions into the second shift region.
 9. The variable camshaft as defined in claim 8 wherein the outer catch wall is operatively configured to engage with the at least one pin in order to stop the axial movement of the axially moveable structure relative to the base shaft while the pin travels straight through the balancing region.
 10. A variable camshaft comprising: a base shaft; an axially movable structure mounted on the base shaft, the axially movable structure being axially movable relative to the base shaft and being rotationally fixed to the base shaft, wherein the axially movable structure includes at least one barrel cam defining a control groove having a first shift region, a balancing region having an outer catch wall, a second shift region, and a disengagement region having a disengagement catch wall; an actuator including an actuator body and at least one pin movably coupled to the actuator body, the at least one pin being configured to move relative to the actuator body between a retracted position and an extended position; and wherein the axially movable structure is configured to move axially relative to the base shaft when the base shaft rotates about a longitudinal axis and the at least one pin is in the extended position and at least partially disposed in one of the first or second shift regions of the control groove.
 11. The variable camshaft as defined in claim 10 wherein the balancing region is defined in the control groove between the first and second shift regions, the balancing having an outer catch wall thickness which is greater than a thickness of the disengagement catch wall.
 12. The variable camshaft as defined in claim 11 wherein the at least one pin is operatively configured to be axially stationary in the balancing region.
 13. The variable camshaft as defined in claim 11 wherein the first shift region defines a first push wall operatively configured to engage with the at least one pin thereby moving the axially moveable structure along the base shaft.
 14. The variable camshaft as defined in claim 13 wherein the disengagement region of the control groove defines a disengagement catch wall.
 15. The variable camshaft as defined in claim 14 wherein the second shift region defines a second push wall operatively configured to engage with the at least one pin thereby moving the axially moveable structure further along the base shaft.
 16. The variable camshaft as defined in claim 15 wherein the outer catch wall and the disengagement catch wall are operatively configured to engage with the at least one pin in order to stop the axial movement of the axially moveable structure relative to the base shaft. 